Bouncy-bouncy is the phenomenon experienced when an up-and-down motion, such as one created by walking, running, or in a best-case scenario, jumping on a trampoline, is exhibited by a female. This causes the chest to bounce up and down in a very entertaining manner.

Bouncy Bouncy is the fancy words for the concept of bounce
The concept of bounce is the law: an object hits the ground at an expotential rate, as it hits the ground, it reverberates and therefore, is pushed into the air by the force if the reverberation